1. Field of the Invention
The present invention relates to a mobile body that moves along a movement path in which a plurality of pairs of magnetic poles, each including a north pole and a south pole, are arranged, by using a linear motor.
2. Description of the Related Art
There has been known a mobile body system including a mobile body having a linear motor and a magnetic pole path in which a plurality of pairs of magnetic poles, each including a north pole and a south pole, are arranged. In this kind of mobile body system, the linear motor is driven by magnetic interaction with a magnetic flux of the magnetic pole path, and the mobile body thereby moves along the magnetic pole path.
Meanwhile, in this kind of mobile body system, a magnetic pole path may have a magnetic pole missing section in which the magnetic pole is missing.
In this respect, there exists a mobile body system in which a mobile body includes two linear motors, two magnet absence detecting sensors (e.g., photo sensors) respectively corresponding to the two linear motors, and two position detecting sensors (e.g., Hall elements) respectively corresponding to the two linear motors. In this mobile body, when one magnet absence detecting sensor detects one linear motor being located in the magnetic pole missing section, switching is made to the other linear motor, to enable continuous driving. Further, in this mobile body, when one position detecting sensor detects one linear motor being located in the magnetic pole missing section, switching is made to the other position detecting sensor, to enable continuous position detection for the mobile body.
Meanwhile, in this kind of mobile body, the magnet absence detecting sensor and the linear motor are offset in a path direction of the magnetic pole path, thus making it difficult for the magnet absence detecting sensor to detect every state of the linear motor being located in the magnetic pole missing section. In particular, when the mobile body is started while the linear motor is located in the magnetic pole missing section, it is not possible to detect the linear motor being located in the magnetic pole missing section, which results in a decrease in thrust of the linear motor and generation of thrust in a reverse direction.